The invention relates to a hydraulic operational system for an injection molding machine and including a hydraulic pump for supplying a hydraulic fluid to hydraulic line network, a plurality of hydraulic drives or cylinders for driving components of the injection molding machine, and a plurality of valves which connect respective hydraulic drives with the hydraulic line network.
The discontinuous operations of the injection molding machine take place in sequence in accordance with separate displacements of the hydraulic drives which are characterized by different displacement paths.
The operation of the injection molding machine requires that the hydraulic flow be adapted to respective different displacements of the hydraulic drives. It is conventional to so influence the displacements of each separate hydraulic cylinder that an acceleration or deceleration of it takes place, in particular, at the beginning and end phases of their displacement. As a result, a non-uniform displacement takes place.
In conventional hydraulic operational systems, different methods and means are employed for controlling the flow of the hydraulic fluid to the hydraulic cylinders. E.g. in some conventional systems, flow control valves are used for bleeding-off a portion of a pump output flow. The flow control valve can also be provided in the main flow in systems that includes an accumulator. Also, hydraulic pumps having a variable flow rate are used in the conventional systems.
However, all known conventional hydraulic operational systems are characterized by a rather poor efficiency. Thus, the pumps with a variable flow rate are characterized by an increased noise, which has to be reduced by employing additional means.
Accordingly, an object of the invention is a hydraulic operational system of the above-described type in which the drawbacks of the conventional hydraulic systems are eliminated.
Another object of the invention is a hydraulic operational system in which the noise is substantially eliminated.
A further object of the invention is to provide a hydraulic operational system having reduced operating costs.